Magnetic helical physical unclonable function measured above flight

ABSTRACT

A helical physical unclonable function is disclosed. The helical physical unclonable function may be used to authenticate a supply item for an imaging device. Measurements of the magnetic field above a helical flight are stored in a non-volatile memory to be used by an imaging device to authenticate the supply item. Other systems and methods are disclosed.

CROSS REFERENCES TO RELATED APPLICATIONS

The following applications are related and were filed contemporaneously:“MAGNETIC HELICAL PHYSICAL UNCLONABLE FUNCTION MEASURED ABOVE FLIGHT”,“MAGNETIC HELICAL PHYSICAL UNCLONABLE FUNCTION MEASURED ADJACENT TOFLIGHT”, “MANUFACTURING A HELICAL PHYSICAL UNCLONABLE FUNCTION”.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates generally to anti-counterfeit systems andmore particularly to physical unclonable functions.

2. Description of the Related Art

Counterfeit printer supplies, such as toner bottles, are a problem forconsumers. Counterfeit supplies may perform poorly and may damageprinters. Printer manufacturers use authentication systems to detercounterfeiters. Physical unclonable functions (PUF) are a type ofauthentication system that implements a physical one-way function.Ideally, a PUF cannot be identically replicated and thus is difficult tocounterfeit. Thus, it is advantageous to maximize the difficulty ofreplicating a PUF to deter counterfeiters. It is also advantageous forthe PUF and PUF reader to be low cost.

SUMMARY

The invention, in one form thereof, is directed to a supply item for animage forming device having a body; a physical unclonable functionlocated on the body configured to rotate about an axis of rotationhaving a shaft centered on the axis of rotation and a helical flighthaving a length wrapped around the shaft, the helical flight has a topsurface furthest away from the axis of rotation, the helical flightcontains magnetized particles that generate a magnetic field above thetop surface having a varying intensity along the length of the helicalflight, the helical flight has a side surface between the shaft and thetop surface; and a non-volatile memory located on the body containing afirst array of numbers corresponding to the intensity of the magneticfield radial to the axis of rotation above the top surface along asection of the length of the helical flight at a first plurality oflocations each at a first fixed distance from the side surface and alsocontaining a digital signature generated from the first array ofnumbers.

The invention, in another form thereof, is directed to a supply item foran image forming device having a body; a physical unclonable functionlocated on the body configured to rotate about an axis of rotationhaving a shaft centered on the axis of rotation, the shaft has a helicalchannel having a length wrapped around the shaft, the shaft containsmagnetized particles that generate a magnetic field above the shafthaving a varying intensity, the helical channel has a side surface; anda non-volatile memory located on the body containing a first array ofnumbers corresponding to the intensity of the magnetic field radial tothe axis of rotation above the shaft along a section of the length ofthe helical channel at a first plurality of locations each at a firstfixed distance from the side surface and also containing a digitalsignature generated from the first array of numbers.

The invention, in yet another form thereof, is directed to a supply itemfor an image forming device having a body; an auger having a spiralflight having magnetized particles that generate a magnetic field abovethe spiral flight having a varying intensity, the auger is rotatablymounted to the body; and a non-volatile memory located on the bodycontaining an array of numbers corresponding to the intensity of themagnetic field above a section of the spiral flight and also containinga digital signature generated from the array of numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thespecification, illustrate several aspects of the present disclosure, andtogether with the description serve to explain the principles of thepresent disclosure.

FIG. 1 is a block diagram of an imaging system including an imageforming device according to one example embodiment.

FIG. 2 is a top view of a helical PUF.

FIG. 3 is a side view of a PUF reader.

FIG. 4 is a top view of a supply item for an imaging device having ahelical PUF.

FIG. 5 is a graph of magnetic field intensity above a helical flight.

FIG. 6 is example values for generating a digital signature.

FIG. 7 is a top view of a helical PUF.

FIG. 8 is a section view of a helical PUF.

FIG. 9 is a section view of a helical PUF.

FIG. 10, FIG. 11, and FIG. 12 are top views of a helical PUF.

FIG. 13 is a top view of a helical PUF.

FIG. 14 is a top view of a helical PUF.

FIG. 15 is a top view of a supply item for an imaging device having ahelical PUF.

FIG. 16 is a flowchart of a method of manufacturing a supply item for animaging device.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings where like numerals represent like elements. The embodimentsare described in sufficient detail to enable those skilled in the art topractice the present disclosure. It is to be understood that otherembodiments may be utilized and that process, electrical, and mechanicalchanges, etc., may be made without departing from the scope of thepresent disclosure. Examples merely typify possible variations. Portionsand features of some embodiments may be included in or substituted forthose of others. The following description, therefore, is not to betaken in a limiting sense and the scope of the present disclosure isdefined only by the appended claims and their equivalents.

Referring to the drawings and particularly to FIG. 1, there is shown ablock diagram depiction of an imaging system 50 according to one exampleembodiment. Imaging system 50 includes an image forming device 100 and acomputer 60. Image forming device 100 communicates with computer 60 viaa communications link 70. As used herein, the term “communications link”generally refers to any structure that facilitates electroniccommunication between multiple components and may operate using wired orwireless technology and may include communications over the Internet.

In the example embodiment shown in FIG. 1, image forming device 100 is amultifunction device (sometimes referred to as an all-in-one (AIO)device) that includes a controller 102, a user interface 104, a printengine 110, a laser scan unit (LSU) 112, one or more toner bottles orcartridges 200, one or more imaging units 300, a fuser 120, a media feedsystem 130 and media input tray 140, and a scanner system 150. Imageforming device 100 may communicate with computer 60 via a standardcommunication protocol, such as, for example, universal serial bus(USB), Ethernet or IEEE 802.xx. Image forming device 100 may be, forexample, an electrophotographic printer/copier including an integratedscanner system 150 or a standalone electrophotographic printer.

Controller 102 includes a processor unit and associated memory 103 andmay be formed as one or more Application Specific Integrated Circuits(ASICs). Memory 103 may be any volatile or non-volatile memory orcombination thereof such as, for example, random access memory (RAM),read only memory (ROM), flash memory and/or non-volatile RAM (NVRAM).Alternatively, memory 103 may be in the form of a separate electronicmemory (e.g., RAM. ROM, and/or NVRAM), a hard drive, a CD or DVD drive,or any memory device convenient for use with controller 102. Controller102 may be, for example, a combined printer and scanner controller.

In the example embodiment illustrated, controller 102 communicates withprint engine 110 via a communications link 160. Controller 102communicates with imaging unit(s) 300 and processing circuitry 301 oneach imaging unit 300 via communications link(s) 161. Controller 102communicates with toner cartridge(s) 200 and non-volatile memory 201 oneach toner cartridge 200 via communications link(s) 162. Controller 102communicates with fuser 120 and processing circuitry 121 thereon via acommunications link 163. Controller 102 communicates with media feedsystem 130 via a communications link 164. Controller 102 communicateswith scanner system 150 via a communications link 165. User interface104 is communicatively coupled to controller 102 via a communicationslink 166. Processing circuitry 121 and 301 may include a processor andassociated memory such as RAM, ROM, and/or non-volatile memory and mayprovide authentication functions, safety and operational interlocks,operating parameters and usage information related to fuser 120, tonercartridge(s) 200 and imaging unit(s) 300, respectively. Controller 102processes print and scan data and operates print engine 110 duringprinting and scanner system 150 during scanning.

Computer 60, which is optional, may be, for example, a personalcomputer, including memory 62, such as RAM, ROM, and/or NVRAM, an inputdevice 64, such as a keyboard and/or a mouse, and a display monitor 66.Computer 60 also includes a processor, input/output (I/O) interfaces,and may include at least one mass data storage device, such as a harddrive, a CD-ROM and/or a DVD unit (not shown). Computer 60 may also be adevice capable of communicating with image forming device 100 other thana personal computer such as, for example, a tablet computer, asmartphone, or other electronic device.

In the example embodiment illustrated, computer 60 includes in itsmemory a software program including program instructions that functionas an imaging driver 68, e.g., printer/scanner driver software, forimage forming device 100. Imaging driver 68 is in communication withcontroller 102 of image forming device 100 via communications link 70.Imaging driver 68 facilitates communication between image forming device100 and computer 60. One aspect of imaging driver 68 may be, forexample, to provide formatted print data to image forming device 100,and more particularly to print engine 110, to print an image. Anotheraspect of imaging driver 68 may be, for example, to facilitate thecollection of scanned data from scanner system 150.

In some circumstances, it may be desirable to operate image formingdevice 100 in a standalone mode. In the standalone mode, image formingdevice 100 is capable of functioning without computer 60. Accordingly,all or a portion of imaging driver 68, or a similar driver, may belocated in controller 102 of image forming device 100 so as toaccommodate printing and/or scanning functionality when operating in thestandalone mode.

Several components of the image forming device 100 are user replaceablee.g. toner cartridge 200, fuser 120, and imaging unit 300. It isadvantageous to prevent counterfeiting these user replaceablecomponents. A PUF 202 may be attached to the toner cartridge 200 toprevent counterfeiting as described below. A PUF reader 203 may beintegrated into the image forming device 100 to verify the authenticityof the PUF 202. Data related to the PUF 202 may reside in non-volatilememory 201.

FIG. 2 shows PUF 202 with a helical flight 210 wrapped around a shaft212. The helical flight 210 and the shaft 212 may be one integratedpart. Alternatively, they may be two separate parts attached together.The PUF 202 has a pair of cylindrical supports 214, 216 that extendlaterally from each end of the PUF 202. In operation, the PUF 202rotates about an axis of rotation 218. The cylindrical supports 214,216, the shaft 212, and the helical flight 210 are centered on the axisof rotation. The helical flight 210 may be referred to as an auger, andthe helical flight 210 may be referred to as a spiral flight.

The helical flight 210 contains magnetized particles that generate amagnetic field above the top surface 220 of the helical flight 210. Themagnetized particles are, for example, flakes of an alloy of neodymium,iron and boron (NdFeB). The shaft 212 may contain magnetized particlesto add complexity to the magnetic field. The PUF 202 may be located on abody of a supply item for an image forming device such as, for example,toner cartridge 200. When the toner cartridge 200 is located in theimage forming device 100, the PUF 202 interfaces with the PUF reader203, which contains a magnetic field sensor 222 mounted to a printedcircuit board (PCB) 224. The PCB 224 also has a locating pin 226.

FIG. 3 shows a side view of the PUF reader 203, including the magneticfield sensor 222, the PCB 224, and the locating pin 226. The locatingpin 226 is taller than the magnetic field sensor 222. When the PUFreader 203 is engaged with the PUF 202, preferably the locating pin 226rides on the shaft 212 and the magnetic field sensor 222 is locatedabove the helical flight 210 without contacting the helical flight 210.The locating pin material and shape may be selected to minimize the dragagainst the PUF 202. Alternatively, the magnetic field sensor 222 mayride on the helical flight 210. The PUF reader 203 is mounted such thatit is free to move in a compliance direction 310 that is preferablyradial to the axis of rotation 218. Preferably, the PUF reader 203 isbiased by a spring against the shaft 212. This mounting compliance helpsaccommodate mechanical and positional tolerances between the PUF 202 andthe PUF reader 203, which improves reliability and reduces manufacturingcosts. The magnetic field sensor 222 may make measurements radial to theaxis of rotation 218 i.e. parallel to the compliance direction 310. Themagnetic field sensor 222 may make measurements parallel to the axis ofrotation 218 i.e. perpendicular to the compliance direction 310. Themagnetic field sensor 222 may make measurements in three orthogonaldirections.

The locating pin 226 is biased against a side surface 230 of the helicalflight 210. The magnetic field sensor 222 follows a measurement path 228along a section of the helical flight 210. The measurement path 228 isat a fixed distance from the side surface 230. The distance between themagnetic field sensor 222 and the locating pin 226 as well as the anglebetween the PUF reader 203 and the helical flight 210 determines thefixed distance.

In operating, the PUF reader 203 is moved parallel to the axis ofrotation 218. The locating pin 226 pushes against the side surface 230,causing the PUF 202 to rotate about the axis of rotation 218. Sine thelocating pin 226 remains in contact with the side surface 230, thepositional accuracy of the measurement path 228 will be excellent. Thisis important, since shifting the measurement path 228 laterally by asmall amount may radically change the magnetic field seen by themagnetic field sensor 222. The helical PUF 202 is superior to a linearPUF since translation of the PUF reader to read the PUF also maintainsthe position of the PUF reader relative to the PUF. Preferably, themagnetic field sensor 222 and locating pin 226 are aligned parallel tothe axis of rotation 218 to prevent a counterfeiter from replacing thehelical PUF 202 with a linear PUF since the locating pin 226 would raisethe magnetic field sensor 222 too far above the linear PUF.

The helical flight 210 has a helix angle 232. Preferably, the helixangle 232 is between thirty degrees and sixty degrees inclusive. If thehelix angle 232 is less than thirty degrees the PUF 202 may bind andfail to rotate. If the helix angle 232 is more than sixty degrees thePUF 202 may fail to maintain contact between the locating pin 226 andthe side surface 230. Preferably, the helix angle 232 is less than sixtydegrees so the maximum helical flight length may be provided for a givenPUF length, since a longer PUF is harder to duplicate than is a shorterPUF.

FIG. 4 shows the helical PUF 202 located on a supply item for an imagingdevice e.g. toner cartridge 200. The toner cartridge 200 has a body 410for holding toner. The helical PUF 202 is rotatably mounted to the bodyby bearings 412, 414 that encircle the cylindrical supports 214, 216.Non-volatile memory 201 is also located on the body 410 and is mountedto a PCB 416 having a column of electrical contact pads 418. Thenon-volatile memory 201 may contain an array of numbers corresponding tothe intensity of the magnetic field along a section of the measurementpath 228. The non-volatile memory 201 may also contain a digitalsignature generated from the array of numbers. To clone the tonercartridge, a counterfeiter must either duplicate a genuine helical PUFand also duplicate the accompanying non-volatile memory, which isdifficult, or the counterfeiter must create a counterfeit helical PUFand also create a properly signed array of measurements corresponding tothe counterfeit PUF, which is also difficult. Thus, the toner cartridge200 is protected from counterfeiting.

FIG. 5 shows a graph 500 of the intensity 510 of an example magneticfield along a section of the measurement path 228. An array of numbers512 corresponds to the magnetic field intensity measured at regularintervals along the path, as shown by dotted lines 514 on the graph.Preferably, the array of numbers 512 are integers to simplifyprocessing. Alternatively, the array of numbers may be, for example,floating point. The numbers in FIG. 5 and FIG. 6 are in hexadecimalformat.

FIG. 6 shows an example of generating a digital signature from the arrayof numbers 512. Other algorithms for generating a digital signature areknown in the art. The digital signature is used by the controller 102 toverify that the PUF data in the non-volatile memory is authentic. Thetoner cartridge's serial number 610 and the array of numbers 512 arecombined to form a message 612. Preferably, the message is encrypted.Alternatively, the message may be unencrypted. For this example, AES-CBCis used (see, for example, RFC3602 “The AES-CBC Cipher Algorithm and ItsUse with IPsec” published by The Internet Society (2003), and NIST(National Institute of Standards) documents FIPS-197 (for AES) and toSP800-38A (for CBC)). The AES key 614 and CBC Initialization Vector (IV)616 are used as is known in the an to generate the encrypted message618. In this example, to sign the encrypted message 618 first themessage is hashed then the hash is encrypted with the private key 620 ofan asymmetric key pair that includes a public key 622. This example usesthe SHA-512 hashing algorithm and Elliptic Curve Digital SignatureAlgorithm (ECDSA) utilizing a P-512 curve key, as is known in the art.Other algorithms are known in the art. The SHA-512 hash 624 of theencrypted message 618 is used to generate an ECDSA P-512 digitalsignature 626. The signature 626 and encrypted message 618 are stored inthe non-volatile memory 201. The image forming device 100 may use thearray of numbers 512 in the encrypted message 618 to verify theauthenticity of the helical PUF 202, and the image forming device 100may use the digital signature 626 to verify the authenticity of thearray of numbers 512. In this way, the image forming device 100 mayverify the authenticity of the toner cartridge 200.

FIG. 7 shows the helical PUF 202. FIG. 8 shows a section view of thehelical PUF 202 cut along cross-section line 710. In this example, theshaft 212 and the helical flight 210 are two separate parts attachedtogether. The helical flight 210 contains magnetized particles 810, 812that generate a magnetic field above the top surface 220 and adjacent tothe side surface 230. The helical flight 210 has a rectangular crosssection. The side surface 230 is planar which improves the locatingtolerance of the locating pin 226. FIG. 9 shows an alternate embodimentwith the helical flight 210 having a semi-circular cross section. Theside surface 230 is curved which reduces the friction between thelocating pin 226 and the helical flight 210. Other helical flight crosssections may be used e.g. triangular, etc.

FIG. 10 shows an alternate embodiment of a helical PUF 1002. The helicalflight is a shaft 1010 that has a helical channel 1050 wrapped aroundthe shaft 1010. The shaft 1010 contains magnetized particles thatgenerate a magnetic field above the shaft 1010 having varying intensity.The helical channel 1050 has a first side surface 1030. The helical PUF1002 is configured to rotate about an axis of rotation 1018. A pair ofcylindrical supports 1014, 1016, the shaft 1010, and the helical channel1015 are centered on the axis of rotation.

In operation, the locating pin 226 of the PUF reader 203 pushes againstthe first side surface 1030, causing the magnetic field sensor 222 tofollow a first measurement path 1028 along a section of the length ofthe helical channel 1050. The first measurement path 1028 is at a firstfixed distance 1052 from the side surface 1030. In this example, the PUFreader 203 is moving from right to left. FIG. 11 shows the helical PUF1002 while the PUF reader 203 is moving from left to right. The locatingpin 226 pushes against a second side surface 1054 of the helical channel1050, causing the magnetic field sensor 222 to follow a secondmeasurement path 1129 located a second fixed distance 1156 from thefirst side surface 1030. The second fixed distance 1156 is shorter thanthe first fixed distance 1052. Thus, a single helical PUF 1002 with asingle PUF reader 203 may measure two different measurement paths byalternating the direction of travel of the PUF reader 203. This makes itmore difficult to counterfeit the helical PUF 1002, since twomeasurement paths must be duplicated. In operation, preferably the PUFreader 203 initially moves by at least the helical channel pitch 1157 tobe sure the locating pin 226 falls into the helical channel. Then, thePUF reader 203 moves in the opposite direction at least a distance equalto the helical channel pitch since the actuator moving the PUF reader203 will be designed to travel at least that distance.

FIG. 12 shows an alternate PUF reader 1203 that may measure along twomeasurement paths 1028, 1228 simultaneously. The PUF reader 1203 has twomagnetic field sensors 1222, 1223 located on opposite sides of alocating pin 1226.

FIG. 13 shows an alternate embodiment of a helical PUF 1302. A helicalchannel 1350 wraps around a shaft having magnetized particles. Thehelical channel 1350 terminates in a stop 1366 at the left end and asecond stop 1368 at the right end 1368. In operation, the PUF reader 203may be moved laterally along the helical PUF 1302 from left to rightuntil the locating pin 226 hits stop 1368. The controller 102 may detectthis event by monitoring drive current to a motor that moves the PUFreader 203. When this event is detected, the controller 102 knows thePUF reader 203 is at a home position relative to the PUF 1302. Knowingthis helps the controller 102 to align data measured along a measurementpath with data stored in the toner cartridge non-volatile memory. Asecond home position may be at stop 1366.

FIG. 14 shows an alternate PUF reader 1472 that measures a magneticfield adjacent to the side surface 1030. The PUF reader 1472 has amagnetic field sensor 1470 that measures the intensity of the magneticfield normal to the side surface 1030 and parallel to the side surface.The PUF reader 1472 touches the side surface 1030 with a pair of spacers1474, 1476. In operation, the PUF reader 1472 is moved parallel to theaxis of rotation to measure a section of the length of the helicalchannel 1050.

FIG. 15 shows an alternate embodiment of a supply item for an imagingdevice e.g. toner cartridge 1500. The toner cartridge 1500 has a body1505 for holding toner. A helical PUF 1502 is configured to slidelaterally along a drive shaft 1580 located on an axis of rotation 1518of the helical PUF 1502. The drive shaft 1580 may be turned by a drivegear 1584 that is coupled to a motor located in the imaging device 100.The helical PUF 1502 is rotatably mounted to the body 1505 by bearings1512, 1515. The drive shaft 1580 has a flat area 1582 which gives thedrive shaft 1580 a “D” shaped cross section i.e. the drive shaft 1580 isa D-shaft. The helical PUF 1502 has a “D” shaped hole around the axis ofrotation 1518 that is larger than the cross section of the drive shaft1580. Thus, the helical PUF 1502 will rotate when the drive shaft 1580is rotated and the helical PUF 1502 is free to slide laterally along thedrive shaft 1580 parallel to the axis of rotation.

The helical PUF 1502 has a helical flight 1510 and a helical channel1550. The helical flight 1510 contains magnetized particles thatgenerate a magnetic field adjacent to the helical flight 1510. A PUFreader 1503, located in the imaging device 100, has a locating pin 1526and a magnetic field sensor 1522. The PUF reader 1503 is fixedly mountedto the imaging device 100. In operation, rotation of the drive shaft1580 causes a side surface of the helical flight 1510 to contact thelocating pin 1526, which causes the helical PUF 1502 to slide laterallyalong the drive shaft 1580. The magnetic field sensor 1522 reads theintensity of the magnetic field along a section of the length of thehelical flight, and the controller 102 compares the measured field to anarray of numbers stored in a non-volatile memory 1501 mounted to thebody 1505. Alternatively, the magnetic field sensor may be located inthe helical channel 1550 and measure along a side surface. Thisembodiment simplifies mounting the PUF reader 1503 since the PUF reader1503 does not require a mechanism to translate laterally along thehelical PUF 1502.

Preferably, the locating pin 1526 is positioned offset from the axis ofrotation 1518 to provide a torque on the helical PUF 1502 relative tothe drive shaft 1580. This torque increases the friction between thehelical PUF 1502 and the drive shaft 1580 to insure continuous contactbetween the locating pin 1526 and the helical flight 1510.

FIG. 16 shows an example embodiment of a method of manufacturing asupply item for an imaging device according to one embodiment. Method1600 creates a supply item that is difficult to counterfeit.

At block 1610, a body is obtained. The body may be, for example,suitable to hold toner for an imaging device. At block 1612, a helicalauger is obtained. The helical auger has a spiral flight havingmagnetized particles generating a magnetic field above the flight havinga varying intensity. At block 1614, a non-volatile memory device isobtained. At block 1616, the non-volatile memory device is attached tothe body. At block 1618, the helical auger is rotatably attached to thebody.

At block 1620, an array of measurements are created by measuring theintensity of the magnetic field along a section of the spiral flight. Atblock 1622, a digital signature is generated from the array ofmeasurements. At block 1624, the array of measurements is stored in thenon-volatile memory device, and the digital signature is stored in thenon-volatile memory device. These blocks may be performed in alternateorders.

The foregoing description illustrates various aspects and examples ofthe present disclosure. It is not intended to be exhaustive. Rather, itis chosen to illustrate the principles of the present disclosure and itspractical application to enable one of ordinary skill in the art toutilize the present disclosure, including its various modifications thatnaturally follow. All modifications and variations are contemplatedwithin the scope of the present disclosure as determined by the appendedclaims. Relatively apparent modifications include combining one or morefeatures of various embodiments with features of other embodiments.

What is claimed is:
 1. A supply item for an image forming devicecomprising: a body; a physical unclonable function located on the bodyconfigured to rotate about an axis of rotation having a shaft centeredon the axis of rotation and a helical flight having a length wrappedaround the shaft, the helical flight has a top surface furthest awayfrom the axis of rotation, the helical flight contains magnetizedparticles that generate a magnetic field above the top surface having avarying intensity along the length of the helical flight, the helicalflight has a side surface between the shaft and the top surface; and anon-volatile memory located on the body containing a first array ofnumbers corresponding to the intensity of the magnetic field radial tothe axis of rotation above the top surface along a section of the lengthof the helical flight at a first plurality of locations each at a firstfixed distance from the side surface and also containing a digitalsignature generated from the first array of numbers.
 2. The supply itemof claim 1, wherein the physical unclonable function is configured toslide laterally along a drive shaft located on the axis of rotation. 3.The supply item of claim 1, wherein the non-volatile memory contains asecond array of numbers corresponding to the intensity of the magneticfield radial to the axis of rotation above the top surface at a secondplurality of locations each located a second fixed distance from theside surface.
 4. The supply item of claim 1, wherein the non-volatilememory contains a third array of numbers corresponding to the intensityof the magnetic field parallel to the axis of rotation above the topsurface along the section of the length of the helical flight at thefirst plurality of locations.
 5. The supply item of claim 1, wherein thehelical flight has a rectangular cross section.
 6. The supply item ofclaim 1, wherein the helical flight has a semi-circular cross section.7. The supply item of claim 1, wherein the section of the length of thehelical flight has a helix angle between thirty degrees and sixtydegrees inclusive.
 8. The supply item of claim 1, wherein the digitalsignature is generated using asymmetric cryptography.
 9. A supply itemfor an image forming device comprising: a body; a physical unclonablefunction located on the body configured to rotate about an axis ofrotation having a shaft centered on the axis of rotation, the shaft hasa helical channel having a length wrapped around the shaft, the shaftcontains magnetized particles that generate a magnetic field above theshaft having a varying intensity, the helical channel has a sidesurface; and a non-volatile memory located on the body containing afirst array of numbers corresponding to the intensity of the magneticfield radial to the axis of rotation above the shaft along a section ofthe length of the helical channel at a first plurality of locations eachat a first fixed distance from the side surface and also containing adigital signature generated from the first array of numbers.
 10. Thesupply item of claim 9, wherein the physical unclonable function isconfigured to slide laterally along a drive shaft located at the axis ofrotation.
 11. The supply item of claim 9, wherein the side surface isplanar.
 12. The supply item of claim 9, wherein the side surface iscurved.
 13. The supply item of claim 9, wherein the section of thelength of the helical channel has a helix angle between thirty degreesand sixty degrees inclusive.
 14. The supply item of claim 9, wherein thenon-volatile memory contains a second array of numbers corresponding tothe intensity of the magnetic field radial to the axis of rotation abovethe shaft at a second plurality of locations each at a second fixeddistance from the side surface.
 15. The supply item of claim 9, whereinthe non-volatile memory contains a third array of numbers correspondingto the intensity of the magnetic field parallel to the axis of rotationabove the shaft along the section of the length of the helical channelat the first plurality of locations.
 16. The supply item of claim 9,wherein the digital signature is generated using asymmetriccryptography.
 17. The supply item of claim 9, wherein the helicalchannel terminates in a stop.
 18. A supply item for an image formingdevice comprising: a body; an auger having a spiral flight havingmagnetized particles that generate a magnetic field above the spiralflight having a varying intensity, the auger is rotatably mounted to thebody; and a non-volatile memory located on the body containing an arrayof numbers corresponding to the intensity of the magnetic field above asection of the spiral flight and also containing a digital signaturegenerated from the array of numbers.
 19. The supply item of claim 18,wherein the spiral flight has a helix angle between thirty degrees andsixty degrees inclusive.
 20. The supply item of claim 18, wherein thedigital signature is generated using asymmetric cryptography.